/*
 * Copyright 2002-2010 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System.Collections;

namespace Spring.Caching;

/// <summary>
/// A simple <see cref="ICache"/> implementation backed by a dictionary that
/// never expires cache items.
/// </summary>
/// <author>Aleksandar Seovic</author>
public class NonExpiringCache : AbstractCache
{
    private readonly object syncRoot = new object();
    private readonly IDictionary<object, object> itemStore = new Dictionary<object, object>();

    /// <summary>
    /// Gets the number of items in the cache.
    /// </summary>
    public override int Count
    {
        get
        {
            lock (syncRoot)
            {
                return itemStore.Count;
            }
        }
    }

    /// <summary>
    /// Gets a collection of all cache item keys.
    /// </summary>
    public override ICollection Keys
    {
        get
        {
            lock (syncRoot)
            {
                return (ICollection) itemStore.Keys;
            }
        }
    }

    /// <summary>
    /// Retrieves an item from the cache.
    /// </summary>
    /// <param name="key">
    /// Item key.
    /// </param>
    /// <returns>
    /// Item for the specified <paramref name="key"/>, or <c>null</c>.
    /// </returns>
    public override object Get(object key)
    {
        lock (syncRoot)
        {
            object value;
            itemStore.TryGetValue(key, out value);
            return value;
        }
    }

    /// <summary>
    /// Removes an item from the cache.
    /// </summary>
    /// <param name="key">
    /// Item key.
    /// </param>
    public override void Remove(object key)
    {
        lock (syncRoot)
        {
            itemStore.Remove(key);
        }
    }

    /// <summary>
    /// Removes collection of items from the cache.
    /// </summary>
    /// <param name="keys">
    /// Collection of keys to remove.
    /// </param>
    public override void RemoveAll(ICollection keys)
    {
        lock (syncRoot)
        {
            foreach (object key in keys)
            {
                itemStore.Remove(key);
            }
        }
    }

    /// <summary>
    /// Removes all items from the cache.
    /// </summary>
    public override void Clear()
    {
        lock (syncRoot)
        {
            itemStore.Clear();
        }
    }

    /// <summary>
    /// Inserts an item into the cache.
    /// </summary>
    /// <param name="key">
    /// Item key.
    /// </param>
    /// <param name="value">
    /// Item value.
    /// </param>
    /// <param name="timeToLive">
    /// Item's time-to-live (TTL) in milliseconds.
    /// </param>
    protected override void DoInsert(object key, object value, TimeSpan timeToLive)
    {
        lock (syncRoot)
        {
            itemStore[key] = value;
        }
    }
}